The Mouse Auditory Testing Core Facility was created in July 2011 to assist the Principle Investigators of the NIDCD and their collaborators with auditory testing in mice. Two techniques that are widely used in evaluating auditory function in mice and other animals are employed at the facility: auditory brainstem response (ABR) testing and distortion-product otoacoustic emissions (DPOAEs). The ABR is an evoked potential that can be used to estimate hearing thresholds. The ABR is recorded by placing electrodes on the scalp and recording the potentials generated by the auditory nervous system when a sound is repeatedly presented to the ear. DPOAEs are soft sounds produced by normally-functioning ears that can be used to screen for hearing loss or to evaluate inner ear function. The presence of DPOAEs indicates normal function of cells in the inner ear (cochlea) called outer hair cells. DPOAEs are measured by placing a small probe containing two speakers and a microphone in the opening of the ear canal. Two tones are played simultaneously to the ear and the DPOAEs produced by the ear are recorded by the microphone. In the first year of operation, we have expanded the number of test suites available to investigators at the NIDCD from one to two. A new system (Tucker-Davis Technologies) is now operational in the second suite and permits measurement of both ABR and DPOAEs over a larger frequency range than was previously possible with existing equipment. A third suite that will be available for testing mice from outside the 5 Research Court facility is nearing completion. We have assisted with data collection and data analysis on eight projects conducted by investigators within the NIDCD and one project conducted by investigators at the NEI. Thus far, 16 investigators have been trained in ABR and DPOAE test techniques and interpretation. A seminar series addressing basic and advanced issues in auditory testing in mice has been initiated and will continue into the next year.